In a G.P. the 9th term is 32805 and 6th term is 1215. Find the 12th term.

Solution :

(2) / (1) ==> ar5/ar8 = 1215/32805

1/r3 = 1/27

(1/r)3 = (1/3)3

r = 3

By applying the value of r in (2), we get

a(3)5 = 1215

a = 1215/35

a = 5(35)/35

a = 5

12th term :

t12 = ar11

t12 = 5(3)11